1. Field of the Invention.
The present invention relates to a mount construction of a wear detection probe for detecting a wear of a brake lining member.
2. Description of the Related Art.
A wear detection probe for a brake lining member of an automotive vehicle detects when wear of the brake lining member has reached its operating limit. A mount construction for such a wear detection probe is disclosed in Japanese Unexamined Utility Model Publication No. 6-30543, and is shown in FIG. 14. The prior art probe of FIG. 14 has a support member 2 formed with a forked raised portion 2B having a curved portion 2A at its leading end. The support member 2 is fixed to the upper surface of a backplate 1 by a set screw 3. A compression spring 5 is accommodated in a mount hole 4 of the backplate 1 and a wear detection probe 6 is inserted into the mount hole 4 of the backplate 1. The wear detection probe 6 has a locking pin 6A that is engaged with the curved portion 2A by the elastic restoring force of the compression spring 5 so as to hold the wear detection probe 6 while restricting it from moving upwardly and downwardly. In this mounted state, the bottom end of the wear detection probe 6 projects downward through the mount hole 4. The lining member 7 and the wear detection probe 6 progressively abrade from the bottom surface of the lining member 7 by contact with a rotor (not shown). A lead wire (not shown) is embedded in the wear detection probe 6 and also will be abraded after sufficient abrasion of the bottom end of the wear detection probe 6 by the rotor. Eventually, the lead wire will be cut by the abrasive action of the rotor to indicate that the lining member 7 has worn to its operating limit.
When the rotor contacts the prior art wear detect ion probe 6, the wear detection probe 6 may instantaneously be subjected to an impact and cut since the rotor is rotating a t high speed. It is desirable that the wear detection probe 6 be moved elastically upwardly in order to cushion the impact. It is also desirable that the lead wire be abraded and cut by the rotor with the wear detection probe 6 elastically held.
On the other hand, since the vertical position of the prior art wear detection probe 6 serves as a detection reference position for the wear limit, the wear detection probe 6 needs to be brought into contact with the rotor while being held in a specified position even after being moved to an uppermost position to cushion the impact.
Since the single raised portion 2B alone provides both the cushioning function and the holding function in the prior art mount construction, the holding function is disadvantageously degraded if the raised portion 2B is made easy to undergo an elastic deformation by prioritizing the cushioning function. Conversely, the cushioning function is disadvantageously degraded if the rigidity of the raised portion 2B is enhanced by prioritizing the holding function.
Further, it is necessary to protect the cushioning function of the raised portion 2B by preventing the raised portion 2B from being excessively deformed beyond its elasticity limit when an external force acts on the lead wire during a mount operation. The prior art mount construction is not provided with such a protection means.
The present invention was developed in view of the above problems, and an object thereof is to attain a function of cushioning an impact given from a rotor to a wear detection probe, a function of holding the wear detection probe in a specified position during the contact with the rotor, and a function of protecting the cushioning function against an external force.
According to the invention, there is provided a mount construction of a wear detection probe that detects when a brake lining member has reached its operating limit. A detection wire is provided in the wear detection probe and is abraded and cut by a rotor to produce a signal indicating that wear of the brake lining has reached its operating limit. The mount construction includes a locking means provided at the wear detection probe. A biasing means is engaged with the locking means for substantially elastically pushing the wear detection probe to receiving means on the brake lining. A stopper means is provided for restricting a backward movement of the wear detection probe. The stopper means is brought substantially into contact with the locking means when the wear detection probe moves backward against a biasing force of the biasing means by the action of an external force.
The flexible rigidity of the biasing means preferably is set smaller than that of the stopper means.
According to a preferred embodiment, a backplate is provided for fixedly supporting the brake lining member and supporting the wear detection probe so as to be movable along forward and backward directions while being located opposite to the rotor.
Preferably, a receiving means is provided or is providable at the backplate for restricting a forward movement of the wear detection probe toward the rotor.
According to a further embodiment, there is provided a mount construction of a wear detection probe that detects when a brake lining member has reached its operating limit. The wear detection probe includes a detection wire that abrades and eventually is cut by a rotor to produce a signal to indicate that the brake lining has reached its operating limit. The mount construction includes a backplate for fixedly supporting the brake lining member and for supporting the wear detection probe so that the wear detection probe is movable along forward and backward directions while being located opposite to the rotor. A receiving means is provided at the backplate for restricting a forward movement of the wear detection probe toward the rotor. A locking means is provided at the wear detection probe, and a biasing means is engageable with the locking means for elastically pushing the wear detection probe to the receiving means. A stopper means is provided for restricting a backward movement of the wear detection probe by contacting the locking means when the wear detection probe moves backward against a biasing force of the biasing means by the action of an external force.
The wear detection probe is subjected to an impact when brought into contact with the rotor. However the wear detection probe is retracted elastically against the biasing force of the biasing means to cushion the impact. The detection wire is abraded and eventually cut by the rotor with the wear detection probe elastically held. The wear detection probe initially may move backward without the detection wire being cut. However, the stopper means limits backward movement, and hence the detection wire is cut with the wear detection probe held in a specified position by the stopper means. Accordingly, a premature breakage of the wear detection probe can be prevented, and a detection reference position for the wear limit can be maintained. Further, since the stopper means prevents the biasing means from being excessively deformed beyond its elasticity limit, the cushioning function of the biasing means can be protected.
Preferably, the biasing means comprises a biasing piece formed at a biasing mount plate fixed to the backplate, and the stopper means comprises a stopper piece formed at a stopper mount plate fixed to the backplate. The thickness of the biasing mount plate is set different from, preferably smaller than, that of the stopper mount plate.
Since the biasing means and the stopper means are formed at the separate mount plates, the cushioning function by the biasing means and the holding function by the stopper means can be performed well and can be set with high degree of freedom. Further, there is less likelihood of losing parts as compared to a case where the biasing means and the stopper means are separate parts from the biasing mount plate and the stopper mount plate and are independently mounted on the backplate without using a fixing means.
Both the biasing means and the stopper means preferably are formed as elastic pieces or projections on a single mount plate, preferably are fixed to the backplate. Additionally the elastic pieces preferably have different lengths. The biasing means may extend in a direction intersecting with the moving direction of the wear detection probe and may have the locking means engaged with the free end thereof. Furthermore the stopper means may project along the moving direction of the wear detection probe and may have the locking means engaged with the free end thereof.
Since the biasing means extends in the direction intersecting the moving direction of the wear detection probe and has the locking means engaged with the free end thereof, it is likely to be elastically deformed and performs a proper cushioning function. On the other hand, since the stopper means projects along the moving direction of the wear detection probe and has the locking means engaged with the free end thereof, it is hard to be elastically deformed and performs a high level of holding function. Further, since only the single mount plate is used, a production cost can be reduced. There is less likelihood of losing parts and the number of parts can be smaller as compared to a case where the biasing means and the stopper means are parts separate from the mount plate and are independently mounted on the backplate.
A plurality of locking means may project in circumferentially spaced positions at the periphery of the wear detection probe. Additionally the biasing means and the stopper means may be arranged in positions circumferentially displaced from each other or substantially corresponding to positions of the respective locking means to interact with (preferably more than two) corresponding locking pins of the wear detection probe.
Since the biasing means and the stopper means are arranged in positions circumferentially displaced from each other, the projecting length of the locking means can be shortened as compared to a case where the biasing means and the stopper means are arranged at the inner and outer sides in the same circumferential position. Further, a space required for arranging the biasing means and the stopper means can be made smaller.
Most preferably, at least one of the biasing means and the stopper means is provided with a loose movement restricting means for permitting the locking means to be displaced to engagement positions with the biasing means and the stopper means as the wear detection probe is rotated and restricting a loose movement of the locking means in the engagement positions.
By providing the loose movement restricting means for the wear detection probe, the locking means can be set on the biasing means and the stopper means and the set state can be maintained securely.
These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings.